A miniaturized infrared athermal fisheye lens

Abstract

The utility model relates to the technical field of optical lenses, specifically a miniaturized infrared athermalized fisheye lens, including a first lens, a second lens, a third lens, a fourth lens, a detector window and an image plane in order from the object side to the image side, the first lens is composed of a meniscus germanium lens with a convex surface facing the object side, the second lens is composed of a biconvex chalcogenide glass, and the third lens has a positive refractive power and is composed of a meniscus germanium lens. The utility model adopts optical athermalization technology, and can clearly image in the temperature range of ‑40°C to +60°C; the lens has a large aperture (F number 1.0) and a large optical light flux, which is conducive to the detection of weak targets; the field of view is large, and the diagonal field of view is 180 degrees; the volume is small and the weight is light, which can effectively reduce the cost, so that it can be well applied to forest fire monitoring, public security, border defense, airport, substation monitoring and other aspects, especially the observation of high-altitude operation drones that require miniaturization.

Description

Technical Field

[0001] The utility model relates to the technical field of optical lenses, in particular to a miniaturized infrared athermal fisheye lens. Background Art

[0002] In recent years, infrared uncooled detectors have become more and more mature, and infrared lenses have been more and more widely used in defense, industry, medical treatment, power detection and other fields. Long-wave infrared fisheye lens is a special lens with a field of view of more than 180 degrees. It is a lens with a small focal length and a large field of view. It plays an important role in forest fire monitoring, public security, border defense, airport, substation monitoring, etc.

[0003] A Chinese patent with publication number CN 108681032 B discloses a large-format long-wave infrared optical passive athermal fisheye lens, including a first lens, a second lens, a third lens and a fourth lens arranged in sequence from the object side to the target surface; wherein the first lens is a negative power lens with the convex surface facing the object side; the second lens is a positive power lens with the convex surface facing the object side; the third lens is a negative power lens with the convex surface facing the object side; and the fourth lens is a positive power lens with the convex surface facing the object side. This solution adopts optical passive athermalization technology, and the diagonal field of view can reach 180°, and the temperature variation range is -40° to +60°. It is suitable for occasions with a large temperature variation range such as forest fire monitoring, public security, and border defense, and has high reliability; the imaging format is large and can be used for 640 movement, and the optical system has a large light throughput.

[0004] A Chinese patent with publication number CN 117741927 A discloses an athermal long-wave infrared fisheye lens. It includes a first lens, a second lens, a third lens, and a fourth lens in order from the object side to the image side; the first lens has a negative refractive power, the object side is a convex surface, the surface type is a spherical surface, and the image side is a concave surface, and the surface type is a spherical surface; the second lens has a negative refractive power, the object side is a convex surface, the surface type is an aspherical surface, and the image side is a concave surface, and the surface type is an aspherical surface; the third lens has a positive refractive power, the object side is a convex surface, the surface type is an aspherical surface, and the image side is a convex surface, and the surface type is a binary diffraction surface; the fourth lens has a positive refractive power, the object side is a concave surface, the surface type is an aspherical surface, and the image side is a convex surface, and the surface type is an aspherical surface. The scheme has a good imaging effect in the long-wave band, is smaller in size than the same type of lens, uses fewer optical elements, and is more economical and practical. The lens of this scheme has a small number of lenses and a simple structure, achieving the purpose of miniaturization of the optical system.

[0005] Existing related technologies often have the following defects: Chinese patent CN 117741927 A discloses an athermalized long-wave infrared fisheye lens, which has a diagonal field of view of 180 degrees and an F number of 1, but is large in size and high in cost. Chinese patent CN 219657942 U discloses a lightweight flight payload large-format athermal wide-angle lens, which has a small size and low cost, but has a diagonal field of view of only 168.9 degrees and an F number of 1.2, with a small luminous flux, which is not conducive to the detection of weak targets.

[0006] Therefore, the utility model provides a miniaturized infrared athermal fisheye lens. Utility Model Content

[0007] The purpose of the utility model is to solve the shortcomings of the prior art that most fisheye lenses are large in size, high in cost, small in luminous flux, not conducive to the detection of weak targets, and the image is greatly affected by high and low temperatures, and to propose a miniaturized infrared athermal fisheye lens.

[0008] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a miniaturized infrared athermal fisheye lens, comprising, from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a detector window and an image plane, wherein the first lens is composed of a meniscus germanium lens with a convex surface facing the object side, the second lens is composed of a biconvex chalcogenide glass, the third lens has positive refractive power and is composed of a meniscus germanium lens, and the fourth lens has positive refractive power and is composed of a meniscus chalcogenide glass.

[0009] Preferably, the first lens comprises an aspherical surface.

[0010] Preferably, the second lens comprises an aspherical surface.

[0011] Preferably, the third lens comprises a diffractive surface and an aspherical surface.

[0012] Preferably, the fourth lens includes an aspherical surface.

[0013] Preferably, the first lens, the second lens, the third lens and the fourth lens utilize aspheric and binary surface DOE technology to correct high-order aberrations, and the lens images are clear, reliable and stable within the temperature range of -40°C to +60°C.

[0014] Preferably, the focal lengths of the first lens, the second lens, the third lens and the fourth lens satisfy the following relationship:

[0015] 3<|f1|<10;

[0016] 10<|f2|<50;

[0017] |f3|>50;

[0018] 5<|f4|<15,

[0019] Among them, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

[0020] In summary:

[0021] In the utility model, optical athermalization technology is adopted, and clear imaging can be achieved in the temperature range of -40°C to +60°C; the lens has a large aperture (F number 1.0) and a large optical light flux, which is conducive to the detection of weak targets; the field of view is large, and the diagonal field of view is 180 degrees; the volume is small and the weight is light, which can effectively reduce the cost, so that it can be well applied to forest fire monitoring, public security, border defense, airport, substation monitoring and other aspects, especially the observation of high-altitude operation drones that require miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an optical schematic diagram of a large aperture, miniaturized, long-wave infrared athermal fisheye lens according to an embodiment of the utility model.

[0023] Figure 2 It is a schematic diagram of the MTF curve of an embodiment of the present invention at +20°C.

[0024] Figure 3 It is a schematic diagram of the MTF curve of an embodiment of the present invention at -40°C.

[0025] Figure 4 It is a schematic diagram of the MTF curve of an embodiment of the present invention at +60°C.

[0026] Figure 5 It is a schematic diagram of field curvature and distortion of an embodiment of the utility model at +20°C.

[0027] Figure 6 It is a schematic diagram of field curvature and distortion of an embodiment of the utility model at -40°C.

[0028] Figure 7 It is a schematic diagram of field curvature and distortion of an embodiment of the utility model at +60°C.

[0029] Legend: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Detector window; 6. Image plane. DETAILED DESCRIPTION

[0030] Reference Figure 1-7As shown, the utility model provides a technical solution: a large aperture miniaturized long-wave infrared athermal fisheye lens, which includes a first lens 1, a second lens 2, a system aperture ST, a third lens 3, a fourth lens 4, a detector window 5 and an image plane 6 in order from the object side to the imaging side. The first lens 1 is composed of a meniscus germanium lens with a convex surface facing the object side, the second lens 2 is composed of a biconvex chalcogenide glass, the third lens 3 has a positive refractive power and is composed of a meniscus germanium lens. The fourth lens 4 has a positive refractive power and is composed of a meniscus chalcogenide glass. The entire lens is composed of four lenses, wherein the first lens 1 includes an aspheric surface, the second lens 2 includes an aspheric surface, the third lens 3 is a diffraction surface and an aspheric surface, and the fourth lens 4 includes an aspheric surface.

[0031] Preferably, the focal lengths of the three lenses satisfy the following relationship:

[0032] 3<|f1|<10;

[0033] 10<|f2|<50;

[0034] |f3|>50;

[0035] 5<|f4|<15.

[0036] Among them, f1 is the focal length of the first lens 1 -6.1, f2 is the focal length of the second lens 2 12.8, f3 is the focal length of the third lens 3 59.8, and f4 is the focal length of the fourth lens 4 8.2.

[0037] Figure 2-Figure 4 This is a schematic diagram of the optical transfer function MTF curve of the infrared optical system at temperatures of +20°C, -40°C, and +60°C, representing the comprehensive resolution level of the optical system as the temperature changes. The horizontal axis represents the spatial frequency of line pairs / mm, and the vertical axis represents the MTF value. With the 640x512 (12μm) detector required to reach a resolution of 42 line pairs, it can be seen from the figure that the infrared optical system has compensated for various aberrations, which is sufficient to meet the optical athermalization requirements.

[0038] Figures 5 to 7 The field curvature and distortion diagrams of this embodiment at temperatures of +20°C, -40°C, and +60°C are shown. It can be seen from the diagram that the curvature of the imaging is relatively good, and the distortion is -100%.

[0039] Table 1 shows the four lenses and the aperture surface of the large aperture miniaturized long-wave infrared athermal fisheye lens of the embodiment. The curvature radius, lens center thickness, lens center distance, lens refractive index, and outer diameter thereof meet the following conditions:

[0040]

[0041] Surface number Face type R (radius of curvature) D(center distance) Nd(refractive index) Outer diameter(mm) 1 Spherical 14.02 3 22 2 Aspheric 6.69 8.46 4 12.8 3 Spherical 42.31 2.8 13.2 4 Aspheric -47.3 2.78 2.78 12.9 5 Aperture Infinity 1.37 6.7 6 Aspheric -12.07 3 4 7.6 7 Spherical -13.59 2.65 10.3 8 Aspheric -283.46 4.2 2.78 16 9 Spherical -13.99 5.8 17 10 flat Infinity 1 4 10.8 11 flat Infinity 1 10.6 12 Image plane Infinity

[0042] The surfaces numbered 2, 4, 6, and 8 in the table are aspherical surfaces. Aspherical lenses satisfy the following formula:

[0043]

[0044] Where: z is the lens sagittal height of the aspherical surface along the optical axis; c = 1 / R, R is the vertex radius of the aspherical surface, r is the semi-aperture of the lens perpendicular to the optical axis, k is the quadratic surface parameter, α2, α3, α4, α5, α6 are the aspherical coefficients. The aspherical surface parameters in this embodiment are shown in Table 2:

[0045]

[0046]

[0047]

[0048] Table 3 shows the diffraction surface coefficients in the embodiments:

[0049]

[0050] surface Diffraction order Central wavelength A1 A2 6 1 1e+004 -0.002 -7.83e-005

[0051] The expression used for the above diffraction surface is: Φ=A1Y 2 +A2Y 4

[0052] The meaning of each quantity in the expression is as follows:

[0053] φ is the phase of the diffraction surface;

[0054] Y is the semi-aperture of the lens perpendicular to the optical axis;

[0055] A1 and A2 are the diffraction surface phase coefficients.

[0056] It can be seen from the embodiment that the utility model large aperture miniaturized long-wave infrared athermal fisheye lens adopts athermal design, large aperture F number is 1.0, and diagonal field angle is 180 degrees. The total optical length is only 36mm, and the lens weight is only 17.1g. It has the advantages of small size and light weight, which can effectively reduce costs, so it can be well applied to forest fire monitoring, public security, border defense, airport, substation monitoring, etc., especially requiring miniaturized high-altitude operation drone observation.

[0057] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

Claims

1. A miniaturized infrared athermal fisheye lens, characterized by: The invention comprises, from the object side to the image side, a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a detector window (5) and an image plane (6), wherein the first lens (1) is composed of a meniscus germanium lens with a convex surface facing the object side, the second lens (2) is composed of a biconvex chalcogenide glass, the third lens (3) has a positive refractive power and is composed of a meniscus germanium lens, and the fourth lens (4) has a positive refractive power and is composed of a meniscus chalcogenide glass.

2. The miniaturized infrared athermal fisheye lens according to claim 1, characterized in that: The first lens (1) comprises an aspherical surface.

3. The miniaturized infrared athermal fisheye lens according to claim 1, characterized in that: The second lens (2) comprises an aspherical surface.

4. The miniaturized infrared athermal fisheye lens according to claim 1, characterized in that: The third lens (3) comprises a diffraction surface and an aspheric surface.

5. The miniaturized infrared athermal fisheye lens according to claim 1, characterized in that: The fourth lens (4) includes an aspherical surface.

6. The miniaturized infrared athermal fisheye lens according to claim 1, characterized in that: The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) utilize aspheric and binary surface DOE technology to correct high-order aberrations, and within a temperature range of -40°C to +60°C, the lens images are clear, reliable and stable.

7. The miniaturized infrared athermal fisheye lens according to claim 1, characterized in that: The focal lengths of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) satisfy the following relationship: 3<|f1|<10； 10<|f2|<50； |f3|>50； 5<|f4|<15， Wherein, f1 is the focal length of the first lens (1), f2 is the focal length of the second lens (2), f3 is the focal length of the third lens (3), and f4 is the focal length of the fourth lens (4).

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